The present invention relates to a method of coating a surface of an elastic body with a continuous layer. The invention may be applied, among others, to the coating of rubber-elastic shaped bodies, for example of silicone rubber, which are to be incorporated as implants into organic tissues. In such a case, a layer of titanium, for example, is initially applied to the shaped body, whereby the compatibility of the implant with the tissue is increased. Another field of application is contact lenses where a suitable non-absorbent coating, such as titanium oxide, is provided as a hydrophilic surface, in order to reduce an irritating effect frequently caused by uncoated contact lenses.
A recurring problem with the coating of elastically deformable bodies in in the adhesion of the applied layers. That is, the coatings tend to tear if the body is later deformed, or may be abraded due to the relative motion between the implant formed by the coated body and the surrounding tissue. Soft implants subjected to frequent deformation are particularly susceptible to abrasion.
To improve the adhesion and resistance to abrasion of layers applied in a vacuum, various measures have been taken.
It is known, for example, that with some plastic substrates, layers applied by cathode sputtering adhere better than those applied by normal evaporation. The recent methods of ion-supported vapor deposition may also be employed to improve the adhesion. Further, it may be useful to provide an adhesive layer between the substrate and the layer which insures compatibility with surrounding tissue, for example to provide a copper layer as an adhesive layer, between a substrate of silicone rubber and a metallic titanium layer as the compatible layer.
None of these prior art measures is satisfactory, however, if elastic bodies are concerned which, during use, are subjected to larger and more frequent deformations, such as implants which must follow the movements of the human body.